1. Field of the Invention
The present invention generally relates to liquid mixing and dispensing systems and, more particularly, to those mixing and dispensing systems used for compositions having rapid curing times.
2. Prior Art
The prior art discloses a number of systems which are used to mix compositions comprising two or more liquid components such as a base liquid and a catalyst. A typical device employs a two-chamber dispenser for mixing liquids together. Another example consists of pumping the material through mechanical mixing devices placed just before the point of application. These devices have generally been too awkward and heavy because the driving mechanism and power source must be supplied to the mixing head. In addition, when the size of the device has been reduced to enhance mobility, the mixing device has to operate at higher speeds to provide effective mixing action. The use of higher speed can produce overheating and the inherent unwanted curing of the materials. A primary disadvantage of these devices is that cleaning is extremely difficult since a composition which includes a catalyst may cure inside of the mechanism which has no appropriate means for purging the composition.
Static mixing devices have been employed to overcome the disadvantages of mechanical means. In these devices, it is common to mount the static mixer near the source of supply and then extend tubing from the mixer to a dispenser. In these types of devices, a long and bulky static mixing chamber is needed to affect proper mixing. The chamber is mounted on a permanent support and the material flowed through a flexible hose to a hand held dispenser. Because the chamber and the flexible hose leading from the chamber is filled with the mixed material, the materials would have to be removed from the respective elements in order that they not cure within the chamber and hose. In order to purge the material from the interior of the system, a substantial amount of base material or solvent is required since the catalyst will still be present in sufficient amounts to require the wasting of base material or the auxiliary solvent.
Another problem which is inherent in the devices disclosed by the prior art is that they fail to provide sufficient means to purge the system if the material being mixed and dispensed has a rapid curing time. As the curing time decreases, it is possible that the material will not flow through the hose and dispenser prior to curing. This can result either in internal curing which can result in damage to or loss of the equipment or will limit the length of the hose leading from the mixing chamber. The present invention substantially resolves the problems which are inherent in the devices taught by the prior art. The present invention employs independent sources of the component liquids. A catalyst is forced through a pressure relief valve to a manifold assembly. The base liquid is coupled directly to the manifold assembly. Both the catalyst and base liquids are under high pressure to provide the force necessary for the mixing and dispensing operations. The coupling of the catalyst to the manifold assembly is through a check valve which will shut off the flow of the liquid when the pressure in the input line is reduced below a specified level. Since a system can be purged by merely running base liquid through the entire system, the operation of the pressure relief valve in the catalyst input line will substantially halt the flow of catalyst through the manifold assembly permitting the mixing chambers, hose and flow gun to be purged of the curing composition in a more efficient, economical and expeditious manner.